DE102022133894A1 - High index substrates - Google Patents

Abstract

The present invention relates to high-index glass substrates with optimized light guiding properties for "augmented reality" and "mixed reality" devices.

Description

The present invention relates to high-index glass substrates with optimized light guiding properties for "augmented reality" and "mixed reality" devices, in particular with a high transmission between the UV band edge and 430 nm the expansion of the visually perceived reality through optical overlays of additional objects, features or information with the help of AR glasses. “Mixed Reality” (“Mixed Reality” or “Mixed Reality”) encompasses environments or systems that mix the natural perception of a user with an artificial (computer-generated) perception.

AR glasses as so-called "near-eye displays" (displays close to the eye) consist of at least one (planar) thin, light-conducting plate into which the image is coupled, transported by total reflections on the glass/air surface and by optical grids or partially reflecting mirrors facets is projected to the pupil of the eye.

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für Totalreflexion muss möglichst klein sein. Dazu muss der Brechungsindex n möglichst groß sein. Die Anhebung des Brechungsindex geht jedoch auch mit einer Beeinträchtigung der Transmissionseigenschaften, insbesondere im blauen Spektralbereich einher. Eine der Aufgaben dieser Erfindung ist daher das Ausbalancieren dieser beiden Faktoren für Glassubstrate für eine optimale Gesamt-Performanz der daraus hergestellten AR-Brillen.In order to be able to image the largest possible apparent field of view, the condition for total reflection must be fulfilled for the largest possible angular range; the critical angle $a_{tOt}=\text{arcsin}\frac{1}{n}$

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for total reflection must be as small as possible. For this purpose, the refractive index n must be as large as possible. However, the increase in the refractive index is also accompanied by an impairment of the transmission properties, particularly in the blue spectral range. One of the objects of this invention is therefore the balancing of these two factors for glass substrates for an optimal overall performance of the AR glasses made therefrom.

The task of the light-guiding plate, which can be made from one or more high-index glass substrates, is to guide light beams from the in-coupling aperture to one or more out-coupling apertures with as little interference as possible. Below we look at glitches that affect brightness, contrast, and color fidelity. This applies to the VIS spectral range visible to the human eye, which ranges from approx. 400 nm to 700 nm. Here, the short-wave, blue range from 430 nm to 480 nm is a technical challenge, since both the sensitivity of the human retina is low and the luminance of the usual microdisplays, i.e. micro-LEDs, micro-OLED and LCOS displays.

The internal transmission τ _i at a wavelength of 460 nm and a layer thickness d of 1 cm is preferably >0.9. The absorption coefficient is then α<0.1/cm. The absorption coefficient α at a wavelength of 460 nm is preferably at most 0.09/cm, at most 0.08/cm, at most 0.07/cm, at most 0.06/cm, at most 0.05/cm, at most 0.04 /cm, or at most 0.03/cm. The absorption coefficient α at a wavelength of 460 nm can be, for example, at least 0.001/cm, at least 0.005/cm, at least 0.01/cm or at least 0.02/cm. The absorption coefficient α at a wavelength of 460 nm can, for example, be in a range from 0.001/cm to <0.1/cm, from 0.001/cm to 0.09/cm, from 0.005/cm to 0.08/cm, from 0.005 /cm to 0.07/cm, from 0.01/cm to 0.06/cm, from 0.01/cm to 0.05/cm, from 0.02/cm to 0.04/cm, or from 0.02/cm to 0.03/cm. The internal transmission τ _i at a wavelength of 460 nm and a layer thickness d of 1 cm can be, for example, more than 0.90, at least 0.91, at least 0.92, at least 0.93, at least 0.94, at least 0.95, at least 0.96, or at least 0.97. The internal transmission τ _i at a wavelength of 460 nm and a layer thickness d of 1 cm can be, for example, at most 0.999, at most 0.995, at most 0.99, or at most 0.98. The internal transmission τ _i at a wavelength of 460 nm and a layer thickness d of 1 cm can, for example, be in a range from >0.90 to 0.999, from 0.91 to 0.999, from 0.92 to 0.995, from 0.93 to 0 .9995, from 0.94 to 0.99, from 0.95 to 0.99, from 0.96 to 0.98, or from 0.97 to 0.98.

When we talk about a "layer thickness", this refers in particular to the thickness of the sample on which the parameter can be measured. The layer thickness does not refer to the actual thickness of the glass article. The thickness of the glass article is not limited to this layer thickness. Rather, the layer thickness can serve as a reference thickness for specifying the internal transmission values.

The terms "refractive index" and "refractive index" are used interchangeably in the present disclosure. The refractive index n _G or the refractive index n _G designate the refractive index at a wavelength of 587 nm. In this context, the "G" stands for "green".

Surprisingly, both the transmission properties in the visible spectral range and the refractive index of the glass n _G can be controlled via the position λ _max of the UV band edge of the glass. This can be expressed by the R number according to the invention. $$R=\left(n_G-1\right)\left(\frac{\text{ln}\left[\frac{{\lambda }_G{}^2-{\lambda }_{min}^2}{{\lambda }_G^2-{\lambda }_{max}^2}\cdot \frac{{\lambda }_{max}^2}{{\lambda }_{min}^2}\right]}{42\text{ln}\left[\frac{{\lambda }_B^2-{\lambda }_{min}^2}{{\lambda }_B^2-{\lambda }_{max}^2}\cdot \frac{{\lambda }_R^2-{\lambda }_{max}^2}{{\lambda }_R^2-{\lambda }_{min}^2}\right]}+\frac{1}{2.8}\right)$$

Here (corresponding to the later application) λ _R =656 nm, λ _G =587 nm and λ _B =486 nm are chosen. For the range of R considered here, the empirically determined wavelength λ _min is almost constant and can be set to 33 nm.

The refractive index is preferably determined with a refractometer, in particular with a V-block refractometer. In particular, samples with a square or approximately square base area (e.g. with dimensions of about 20 mm x 20 mm x 5 mm) can be used. When measuring with a V-block refractometer, the samples are usually placed in a V-shaped block prism with a known refractive index. The refraction of an incident light beam depends on the difference between the refractive index of the sample and the refractive index of the V-block prism, so the refractive index of the sample can be determined. The measurement is preferably carried out at a temperature of 22°C.

Surprisingly, glasses only show optimal properties in a narrow range of R: For large R numbers, the possible field of view increases significantly, but the transmission in the blue spectral range suffers, which leads to an overall darkening of the image transmitted through the substrate. In addition, particularly when using chromatically corrected coupling and decoupling optics (e.g. by means of meta-structures), significant color-dependent distortion effects occur in the transverse or longitudinal direction at the edge of the image. For small R numbers, the images are transmitted through the glass more brightly and without interference, but the apparent field of view is significantly narrower. This means that the image section with the virtual objects is significantly smaller for the viewer than the field of view of the real image. The immersion suffers from the cutting off (the so-called "clipping") of the virtual objects at the apparent edge of the field of view. Therefore, glasses with an R number in a range from 0.900 to 1.050, from 0.905 to 1.045, from 0.910 to 1.040, from 0.915 to 1.035, from 0.920 to 1.030, from 0.925 to 1.025, from 0.930 to 1.020, from 0.93 5 to 1.015 , from 0.940 to 1.010, from 0.945 to 1.005, from 0.950 to 1.000, from 0.955 to 0.995, from 0.960 to 0.990, or from >0.965 to <0.985. The R number is preferably at least 0.900, at least 0.905, at least 0.910, at least 0.915, at least 0.920, at least 0.925, at least 0.930, at least 0.935, at least 0.940, at least 0.945, at least 0.950, at least 0.955, at least 0.960, or more preferably > 0.965 . The R number is preferably at most 1.050, at most 1.045, at most 1.040, at most 1.035, at most 1.030, at most 1.025, at most 1.020, at most 1.015, at most 1.010, at most 1.005, at most 1.000, at most 0.995, at most 0.99 0, or particularly preferred < 0.985. An R number in a range from >0.965 to <0.985 is particularly advantageous.

To determine the R number, the UV band edge λ _max must be determined. Although a direct measurement in the UV range can be carried out with existing measuring devices (eg Perkin Elmer Lambda 900), it is technically very complex for two reasons. On the one hand, the measurement must be carried out in a vacuum, otherwise the UV radiation will be absorbed by the air molecules. On the other hand, the absorption of the glasses in this wavelength range is so great that the glass samples have to be ground down very thin in order to achieve a meaningful signal-to-noise ratio in transmission measurements.

Instead of directly measuring the course of the spectral absorption in the vacuum UV (VAV), i.e. in the wavelength range from 10 nm to 200 nm, this wavelength range can be interpolated approximately by using the Kramers-Kronig relations. This is achieved by approximating the VAV absorption using a box profile. Based on the Kramers-Kronig relations, the following relationship to the refractive index in the visible spectral range can then be established: $$n\left(\lambda \right)=c\cdot \text{ln}\left[\frac{{\lambda }^2-{\lambda }_{min}^2}{{\lambda }^2-{\lambda }_{max}^2}\cdot \frac{{\lambda }_{max}^2}{{\lambda }_{min}^2}\right]+1.$$

The following method for determining the band edge λ _max is therefore based on a measurement of the refractive index in the visible.

There are several methods available for measuring the refractive index of glasses in the visible range; the most common is the above-mentioned V-block method for cost-effective measurement up to 5 valid decimal places. For even more accurate measurements, minimum deflection goniometers are typically used for a variety of wavelengths; this achieves an accuracy of up to 6 decimal places. The Abbe refractometer or prism coupler (e.g. from Metricon, model 2020) can be used for quick routine measurements; the achievable accuracy is 4 decimal places. With each of the measurement methods mentioned, the measurement is preferably carried out at a temperature of 22°C.

First, the refractive index must be determined at at least three wavelengths λ ₁ , λ ₂ , λ ₃ in the spectral range from 400 nm to 1000 nm using one of the methods mentioned. From this, the parameters λ _max and c can be determined in a determinate manner by adapting/fitting equation 1. This is done using the least squares method, ie with the refractive indices n _i measured at the wavelengths λ _i

Σ _i (n _i -n(λ _i )) ² →0 minimized, where according to equation 1 $n\left(\lambda \right)=c\cdot \text{ln}\left[\frac{{\lambda }^2-{\lambda }_{min}^2}{{\lambda }^2-{\lambda }_{max}^2}\cdot \frac{{\lambda }_{max}^2}{{\lambda }_{min}^2}\right]+1\text{is}.$

The refractive index is preferably determined at exactly three wavelengths λ ₁ , λ ₂ , λ ₃ in the spectral range from 400 nm to 1000 nm, with λ ₁ = 486 nm, λ ₂ = 587 nm and λ ₃ = 656 nm or λ ₁ = 441 in particular nm, λ ₂ = 639 nm and λ ₃ = 947 nm.

The parameter λ _min = 33 nm is assumed to be constant.

The object is solved by the subject matter of the patent claims.

berechnet wird, wobei λ_R= 656 nm, λ_G = 587 nm und λ_B = 486 nm sind, wobei λ_min = 33 nm ist und wobei n_G der Brechungsindex bei einer Wellenlänge von 587 nm ist.The object is achieved in particular by a glass article with a refractive index n _G ≥1.95 and an R number in a range from 0.900 to 1.050, the R number with $$R=\left(n_G-1\right)\left(\frac{\text{ln}\left[\frac{{\lambda }_G{}^2-{\lambda }_{min}^2}{{\lambda }_G^2-{\lambda }_{max}^2}\cdot \frac{{\lambda }_{max}^2}{{\lambda }_{min}^2}\right]}{42\text{ln}\left[\frac{{\lambda }_B^2-{\lambda }_{min}^2}{{\lambda }_B^2-{\lambda }_{max}^2}\cdot \frac{{\lambda }_R^2-{\lambda }_{max}^2}{{\lambda }_R^2-{\lambda }_{min}^2}\right]}+\frac{1}{2.8}\right)$$

where λ _R = 656 nm, λ _G = 587 nm and λ _B = 486 nm, where λ _min = 33 nm and where n _G is the refractive index at a wavelength of 587 nm.

The present invention is not limited to any particular glass composition. However, the compositions described below have proven to be particularly advantageous. The increase in the refractive index n _G according to the invention can be achieved in particular by the components La ₂ O ₃ , Nb ₂ O ₅ , TiO ₂ , Gd ₂ O ₃ and/or ZrO ₂ . According to the invention, the band edge of the entire glass λ _max can be kept particularly low. Adjusting the sum of the proportions of La ₂ O ₃ , Y ₂ O ₃ , Gd ₂ O ₃ , Yb ₂ O ₃ and Lu ₂ O ₃ has proven particularly advantageous for adjusting the R number. In particular, the R number can be achieved by increasing the proportion of one or more of these components. Other otherwise customary oxides, on the other hand, are advantageously not used or only used in small proportions, for example Al ₂ O ₃ , CaO, K ₂ O, SrO, WO ₃ and/or Ta ₂ O ₅ . However, components such as BaO, WO ₃ , alkalis, other alkaline earths and/or ZnO can be used (in some cases preferably in small amounts) in order to increase the entropy in the system and thus the glass formation.

Preferred components for glass formation are SiO ₂ and/or B ₂ O ₃ . The sum of the proportions of SiO ₂ and B ₂ O ₃ is preferably greater than 0 mol % and is in particular at least 3.5 mol %. The sum of the proportions of SiO ₂ and B ₂ O ₃ is preferably at least 5.0 mol %, at least 7.5 mol %, at least 8.0 mole %, more than 8.0 mole %, at least 9.0 mole % or at least 10.0 mole %. The sum of the proportions of SiO ₂ and B ₂ O ₃ can be, for example, at most 27.5 mol %, at most 25.0 mol %, at most 22.5 mol %, at most 20.0 mol %, less than 20.0 mole %, at most 19.0 mole %, at most 18.0 mole %, at most 17.5 mole %, at most 17.0 mole % or at most 16.5 mole %. The sum of the proportions of SiO ₂ and B ₂ O ₃ can be, for example, in a range from >0 mole % to 27.5 mole %, from 3.5 mole % to 25.0 mole %, from 5.0 mole % to 22.5 mole %, from 7.5 mole % to 20.0 mole %, from 8.0 mole % to 19.0 mole %, from >8.0 mole % to 18.0 mol%, from 9.0 mol% to 18.0 mol%, from 10.0 mol% to 17.5 mol%, from 10.0 mol% to 17.0 mol% % or from 10.0 mole% to 16.5 mole%.

SiO ₂ is a glass former. The component contributes to chemical resistance. If it is used in very large amounts, the refractive indices according to the invention cannot be achieved. The glass preferably contains SiO ₂ in a proportion of from 1.0 mol % to 19.0 mol %, from 1.0 mol % to 18.0 mol %, from 1.0 mol % to 16.5 mol % mole %, from 1.5 mole % to 16.0 mole %, from 2.0 mole % to 16.0 mole %, from 2.5 mole % to 15.5 mole %, or from 3.0 mole percent to 15.0 mole percent. The proportion of SiO ₂ can be, for example, at least 1.0 mol %, at least 1.5 mol %, at least 2.0 mol %, at least 2.5 mol % or at least 3.0 mol %. The proportion of SiO ₂ can be, for example, at most 19.0 mol %, at most 18.0 mol %, at most 16.5 mol %, at most 16.0 mol %, at most 15.5 mol % or at most 15 0 mol%.

B ₂ O ₃ also acts as a glass former. The proportion of B ₂ O ₃ is preferably in a range from 0.0 mol % to 19.0 mol %, from 0.0 mol % to 17.0 mol %, from 0.0 mol % to 15.0 mol%, from 0.0 mol% to 13.5 mol%, from 0.5 mol% to 13.0 mol%, from 1.0 mol% to 12.5 mol% , from 1.5 mole% to 12.0 mole%, or from 2.0 mole% to 12.0 mole%. The proportion of B ₂ O ₃ can be, for example, at least 0.5 mol %, at least 1.0 mol %, at least 1.5 mol % or at least 2.0 mol %. The proportion of B ₂ O ₃ can be, for example, at most 19.0 mol %, at most 17.0 mol %, at most 15.0 mol %, at most 13.5 mol %, at most 13.0 mol %, at most 12.5 mol% or at most 12.0 mol%. In some embodiments, the proportion of B ₂ O ₃ may be at most 10.0 mole %, at most 7.5 mole %, at most 5.0 mole %, at most 2.5 mole % or at most 1.0 mole %. % may be limited or the glass may be B ₂ O ₃ free.

An addition of BaO, along with other components, can increase the entropy in the glass system and thus contribute to glass formation. The presence of BaO in the glass can also be helpful in making the viscosity higher and steeper in the high-viscosity range from around 10 ⁶ dPas to 10 ¹⁴ dPas. In connection with glass systems with a particularly high refractive index, however, BaO can have a refractive index-reducing effect in particularly large proportions. Preferably, the glass contains BaO in a proportion of 1.0 mol% to 20.0 mol%, from 2.0 mol% to 18.0 mol%, from 3.0 mol% to 17.0 mol% -% or from 4.0 mole% to 16.0 mole%. The proportion of BaO can be, for example, at least 1.0 mol%, at least 2.0 mol%, at least 3.0 mol% or at least 4.0 mol%. The proportion of BaO can be, for example, at most 20.0 mol%, at most 18.0 mol%, at most 17.0 mol% or at most 16.0 mol%. In some embodiments, the BaO content may be limited to at most 10.0 mol%, at most 7.5 mol%, at most 5.0 mol%, at most 2.5 mol%, or at most 1.0 mol% or the glass can be free of BaO.

La ₂ O ₃ is one of the components with which the band edge λ _max can be kept particularly low and a particularly high R number can be achieved. In addition, the refractive index n _G can be increased by using La ₂ O ₃ . The glass preferably contains La ₂ O ₃ in a proportion of 5.0 mol % to 20.0 mol %, from 7.0 mol % to 18.0 mol %, from 8.0 mol % to 17 .0 mole % or from 8.5 mole % to 16.0 mole %. The proportion of La ₂ O ₃ can be, for example, at least 5.0 mol %, at least 7.0 mol %, at least 8.0 mol % or at least 8.5 mol %. The proportion of La ₂ O ₃ can be, for example, at most 20.0 mol %, at most 18.0 mol %, at most 17.0 mol % or at most 16.0 mol %.

Nb ₂ O ₅ is one of the components with which the refractive index n _G can be increased. The glass preferably contains Nb ₂ O ₅ in a proportion of from 0.1 mol % to 20.0 mol %, from 0.5 mol % to 18.0 mol %, from 1.0 mol % to 17 .0 mole % or from 2.0 mole % to 16.0 mole %. The proportion of Nb ₂ O ₅ can be, for example, at least 0.1 mol %, at least 0.5 mol %, at least 1.0 mol % or at least 2.0 mol %. The proportion of Nb ₂ O ₅ can be, for example, at most 20.0 mol %, at most 18.0 mol %, at most 17.0 mol % or at most 16.0 mol %.

TiO ₂ is one of the components with which the refractive index n _G can be increased. The glass preferably contains TiO ₂ in a proportion of 28.0 mol % to 65.0 mol %, 30.0 mol % to 62.5 mol %, 32.0 mol % to 60.0 mol % mole % or from 34.0 mole % to 59.0 mole %. The proportion of TiO ₂ can be, for example, at least 28.0 mol %, at least 30.0 mol %, at least 32.0 mol % or at least 34.0 mol %. The proportion of TiO ₂ can be, for example, at most 65.0 mol %, at most 62.5 mol %, at most 60.0 mol % or at most 59.0 mol %.

ZrO ₂ is one of the components with which the refractive index n _G can be increased. The glass preferably contains ZrO ₂ in a proportion of 1.0 mol % to 11.0 mol %, 2.0 mol % to 10.0 mol %, 3.0 mol % to 9.5 mol % mole % or from 4.0 mole % to 9.0 mole %. The proportion of ZrO ₂ can be, for example, at least 1.0 mol %, at least 2.0 mol %, at least 3.0 mol % or at least 4.0 mol %. The proportion of ZrO ₂ can be, for example, at most 11.0 mol %, at most 10.0 mol %, at most 9.5 mol % or at most 9.0 mol %.

Gd ₂ O ₃ is one of the components with which the band edge λ _max can be kept particularly low and a particularly high R number can be achieved. In addition, the refractive index n _G can be increased by using Gd ₂ O ₃ . The proportion of Gd ₂ O ₃ is preferably in a range from 0.0 mol % to 8.0 mol %, from 0.0 mol % to 7.0 mol %, from 0.0 mol % to 6.0 mol%, from 0.0 mol% to 5.0 mol%, from 0.1 mol% to 7.0 mol%, from 0.5 mol% to 6.0 mol% % or from 1.0 mole% to 5.0 mole%. The proportion of Gd ₂ O ₃ can be, for example, at least 0.1 mol %, at least 0.5 mol % or at least 1.0 mol %. The proportion of Gd ₂ O ₃ can be, for example, at most 8.0 mol%, at most 7.0 mol%, at most 6.0 mol% or at most 5.0 mol%. In some embodiments, the proportion of Gd ₂ O ₃ can be at most 4.0 mol %, at most 3.0 mol %, at most 2.0 mol %, at most 1.0 mol % or at most 0.5 mol %. % may be limited or the glass may be Gd ₂ O ₃ free.

Y ₂ O ₃ is one of the components with which the band edge λ _max can be kept particularly low and a particularly high R number can be achieved. The proportion of Y ₂ O ₃ is preferably in a range from 0.0 mol % to 5.0 mol %, from 0.0 mol % to 4.0 mol %, from 0.0 mol % 3 .0 mole %, from 0.0 mole % to 2.0 mole %, or from 0.1 mole % to 4.0 mole %, from 0.2 mole % to 3.0 mole % % or from 0.5 mole% to 2.0 mole%. The proportion of Y ₂ O ₃ can be, for example, at least 0.1 mol %, at least 0.2 mol % or at least 0.5 mol %. The proportion of Y ₂ O ₃ can be, for example, at most 5.0 mol%, at most 4.0 mol%, at most 3.0 mol% or at most 2.0 mol%. In some embodiments, the level of Y ₂ O ₃ may be limited to at most 1.5 mole %, at most 1.0 mole %, at most 0.5 mole %, or at most 0.2 mole %, or the glass may be free _{of Y2O3} .

An addition of ZnO can, in addition to other components, increase the entropy in the glass system and thus contribute to glass formation. The proportion of ZnO is preferably in a range from 0.0 mol % to 5.0 mol %, from 0.0 mol % to 4.0 mol %, from 0.0 mol % to 3.0 mole %, from 0.0 to 2.0 mole %, or from 0.1 mole % to 4.0 mole %, from 0.2 mole % to 3.0 mole %, or from 0, 5 mole% to 2.0 mole%. The proportion of ZnO can be, for example, at least 0.1 mol %, at least 0.2 mol % or at least 0.5 mol %. The proportion of ZnO can be, for example, at most 5.0 mol%, at most 4.0 mol%, at most 3.0 mol% or at most 2.0 mol%. In some embodiments, the amount of ZnO may be limited to at most 1.5 mole %, at most 1.0 mole %, at most 0.5 mole %, or at most 0.2 mole %, or the glass may be free of ZnO .

The addition of WO ₃ can increase the entropy in the glass system, along with other components, and thus contribute to glass formation. The proportion of WO ₃ is preferably in a range from 0.0 mol % to 5.0 mol %, from 0.0 mol % to 4.0 mol %, from 0.0 mol % to 3 0 mole %, from 0.0 mole % to 2.0 mole %, from 0.1 mole % to 4.0 mole %, from 0.2 mole % to 3.0 mole % or from 0.5 mole% to 2.0 mole%. The proportion of WO ₃ can be, for example, at least 0.1 mol %, at least 0.2 mol % or at least 0.5 mol %. The proportion of WO ₃ can, for example, be at most 5.0 mol%, at most 4.0 mol%, at most 3.0 mol% or at most 2.0 mol%, in particular at most 1.5 mol%, at most 1 .0 mol%, at most 0.5 mol% or at most 0.2 mol%. The glass is preferably free of WO ₃ .

Al ₂ O ₃ contributes to glass formation. The proportion of Al ₂ O ₃ is preferably in a range from 0.0 mol % to 3.0 mol %, for example from 0.0 to 2.5 mol %, from 0.0 to 2.0 mol % %, from 0.0 to 1.5 mol%, or from 0.1 mol% to 2.5 mol%, from 0.2 mol% to 2.0 mol%, or from 0.5 mol% -% to 1.5 mol%. The proportion of Al ₂ O ₃ can be, for example, at least 0.1 mol %, at least 0.2 mol % or at least 0.5 mol %. The proportion of Al ₂ O ₃ can be, for example, at most 3.0 mol %, at most 2.5 mol %, at most 2.0 mol % or at most 1.5 mol %, in particular at most 1.2 mol %. , at most 1.0 mol%, at most 0.5 mol% or at most 0.2 mol%. The glass is preferably free of Al ₂ O ₃ .

An addition of CaO, along with other components, can increase the entropy in the glass system and thus contribute to glass formation. The proportion of CaO is preferably in a range from 0.0 mol % to 1.5 mole %, from 0.0 mole % to 1.2 mole %, from 0.0 mole % to 1.0 mole %, from 0.0 mole % to 0.8 mole %, or from 0.1 mole% to 1.2 mole%, from 0.2 mole% to 1.0 mole% or from 0.5 mole% to 0.8 mole%. The proportion of CaO can be, for example, at least 0.1 mol%, at least 0.2 mol% or at least 0.5 mol%. The proportion of CaO can, for example, be at most 1.5 mol%, at most 1.2 mol%, at most 1.0 mol% or at most 0.8 mol%, in particular at most 0.5 mol% or at most 0, 2 mol%. The glass is preferably free of CaO.

An addition of SrO can, in addition to other components, increase the entropy in the glass system and thus contribute to glass formation. The proportion of SrO is preferably in a range from 0.0 mol % to 1.5 mol %, from 0.0 mol % to 1.2 mol %, from 0.0 mol % to 1.0 mole %, from 0.0 mole % to 0.8 mole %, or from 0.1 mole % to 1.2 mole %, from 0.2 mole % to 1.0 mole %, or from 0.5 mole% to 0.8 mole%. The proportion of SrO can be, for example, at least 0.1 mol %, at least 0.2 mol % or at least 0.5 mol %. The proportion of SrO can, for example, be at most 1.5 mol%, at most 1.2 mol%, at most 1.0 mol% or at most 0.8 mol%, in particular at most 0.5 mol% or at most 0, 2 mol%. The glass is preferably free of SrO.

An addition of K ₂ O, along with other components, can increase the entropy in the glass system and thus contribute to glass formation. The proportion of K ₂ O is preferably in a range from 0.0 mol % to 1.5 mol %, from 0.0 mol % to 1.2 mol %, from 0.0 mol % to 1 .0 mole %, from 0.0 mole % to 0.5 mole %, or from 0.1 mole % to 1.0 mole %, or from 0.2 mole % to 0.5 mole % %. The proportion of K ₂ O can be, for example, at least 0.1 mol % or at least 0.2 mol %.

The proportion of K ₂ O can be, for example, at most 1.5 mol%, at most 1.2 mol%, at most 1.0 mol% or at most 0.8 mol%, in particular at most 0.5 mol% or at most 0.2 mol%. The glass is preferably free of K ₂ O.

The proportion of Ta ₂ O ₅ is preferably in a range from 0.0 mol % to 1.5 mol %, from 0.0 mol % to 1.2 mol %, from 0.0 mol % to 1 .0 mole %, from 0.0 mole % to 0.5 mole %, from 0.1 mole % to 1.0 mole %, or from 0.2 mole % to 0.5 mole % %. The proportion of Ta ₂ O ₅ can be, for example, at least 0.1 mol % or at least 0.2 mol %. The proportion of Ta ₂ O ₅ can be, for example, at most 1.5 mol%, at most 1.2 mol%, at most 1.0 mol% or at most 0.8 mol%, in particular at most 0.5 mol%. or at most 0.2 mol%. The glass is preferably free of Ta ₂ O ₅ .

Yb ₂ O ₃ is one of the components with which the band edge λ _max can be kept particularly low and a particularly high R number can be achieved. The proportion of Yb ₂ O ₃ is preferably in a range from 0.0 mol % to 1.5 mol %, from 0.0 mol % to 1.2 mol %, from 0.0 mol % to 1.0 mole%, from 0.0 mole% to 0.5 mole%, or from 0.1 mole% to 1.0 mole%, or from 0.2 mole% to 0.5 mole% -%. The proportion of Yb ₂ O ₃ can be, for example, at least 0.1 mol % or at least 0.2 mol %. The proportion of Yb ₂ O ₃ can be, for example, at most 1.5 mol%, at most 1.2 mol%, at most 1.0 mol% or at most 0.8 mol%, in particular at most 0.5 mol%. or at most 0.2 mol%. The glass is preferably free from Yb ₂ O ₃ .

Lu ₂ O ₃ is one of the components with which the band edge λ _max can be kept particularly low and a particularly high R number can be achieved. The proportion of Lu ₂ O ₃ is preferably in a range from 0.0 mol % to 5.0 mol %, from 0.0 mol % to 4.0 mol %, from 0.0 mol % to 3.0 mol%, from 0.0 mol% to 2.0 mol%, or from 0.1 mol% to 4.0 mol%, from 0.2 mol% to 3.0 mol% or from 0.5 mole percent to 2.0 mole percent. The proportion of Lu ₂ O ₃ can be, for example, at least 0.1 mol %, at least 0.2 mol % or at least 0.5 mol %. The proportion of Lu ₂ O ₃ can be, for example, at most 5.0 mol %, at most 4.0 mol %, at most 3.0 mol % or at most 2.0 mol %, in particular at most 1.5 mol %, at most 1.0 mol%, at most 0.5 mol% or at most 0.2 mol%. The glass is preferably free of Lu ₂ O ₃ .

The targeted setting of the sum of the proportions of La ₂ O ₃ , Y ₂ O ₃ , Gd ₂ O ₃ , Yb ₂ O ₃ and Lu ₂ O ₃ has proven particularly advantageous. The sum of the proportions of La ₂ O ₃ , Y ₂ O ₃ , Gd ₂ O ₃ , Yb ₂ O ₃ and Lu ₂ O ₃ is preferably in a range from 12.5 mol % to 20.0 mol % preferably from 13.5 mole% to 19.0 mole%, more preferably from 14.0 mole% to 18.0 mole%, more preferably from 14.5 mole% to 17.5 mole%. The sum of the proportions of La ₂ O ₃ , Y ₂ O ₃ , Gd ₂ O ₃ , Yb ₂ O ₃ and Lu ₂ O ₃ in is preferably at least 12.5 mol %, more preferably at least 13.5 mol %, further preferably at least 14.0 mole %, more preferably at least 14.5 mole %. The sum of the proportions of La ₂ O ₃ , Y ₂ O ₃ , Gd ₂ O ₃ , Yb ₂ O ₃ and Lu ₂ O ₃ is preferably at most 20.0 mol%, more preferably at most 19.0 mol%, further preferably at most 18.0 mol%, more preferably at most 17.5 mol%.

It has also proven advantageous if the sum of the proportions of SiO ₂ and B ₂ O ₃ is approximately equal to the sum of the proportions of La ₂ O ₃ , Y ₂ O ₃ , Gd ₂ O ₃ , Yb ₂ O ₃ and Lu ₂ corresponds to O ₃ . The ratio of the sum of the contents of SiO ₂ and B ₂ O ₃ (in mol%) to the sum of the contents of La ₂ O ₃ , Y ₂ O ₃ , Gd ₂ O ₃ , Yb ₂ O ₃ and Lu ₂ O ₃ ( in mol %) is preferably in a range from 0.5:1 to 1.3:1, or from 0.5:1 to 1.2:1, in particular in a range from 0.6:1 to 1, 1:1, from 0.7:1 to 1.1:1, from 0.8:1 to 1.1:1 or from 0.9:1 to 1.1:1. The ratio of the sum of the contents of SiO ₂ and B ₂ O ₃ (in mol%) to the sum of the contents of La ₂ O ₃ , Y ₂ O ₃ , Gd ₂ O ₃ , Yb ₂ O ₃ and Lu ₂ O ₃ ( in mol%) can be, for example, at least 0.5:1, at least 0.6:1, at least 0.7:1, at least 0.8:1 or at least 0.9:1. The ratio of the sum of the contents of SiO ₂ and B ₂ O ₃ (in mol%) to the sum of the contents of La ₂ O ₃ , Y ₂ O ₃ , Gd ₂ O ₃ , Yb ₂ O ₃ and Lu ₂ O ₃ ( in mol %) can be, for example, at most 1.3:1, at most 1.2:1 or at most 1.1:1. The ratio of the sum of the proportions of SiO ₂ and B ₂ O ₃ (in mol %) to the sum of the proportions of La ₂ O ₃ , Y ₂ O ₃ , Gd ₂ O ₃ , Yb ₂ O ₃ and Lu ₂ is particularly preferred O ₃ (in mole %) about 1:1, especially from 0.95:1 to 1.05:1. The ratio of the sum of the proportions of SiO ₂ and B ₂ O ₃ (in mol%) to the sum of the proportions of La ₂ O ₃ , Y ₂ O ₃ , Gd ₂ O ₃ , Yb ₂ O ₃ and Lu ₂ O ₃ (in Mol %) can be, for example, at least 0.95:1 and/or at most 1.05:1.

When it is stated in this description that the glasses are free of a component or do not contain a certain component, this means that this component may at most be present in the glasses as an impurity. This means that it is not added in significant amounts. Insubstantial amounts according to the invention are amounts of less than 1000 ppm (molar), or less than 300 ppm (molar), preferably less than 100 ppm (molar), more preferably less than 50 ppm (molar) and most preferably less than 10 ppm (molar) or less than 5 ppm (molar).

The glasses are preferably free of components that are not disclosed as glass components in the present disclosure or contain such components in a total proportion of at most 3.0 mol%, at most 2.0 mol%, at most 1.0 mol%, at most 0.5 mol% or at most 0.2 mol%. In particular, the glasses are preferably free from Fe ₂ O ₃ , Li ₂ O, Na ₂ O, MgO and/or Pt.

The glass article can in particular comprise or consist of a glass which comprises or consists of the following components in the specified proportions (in mol %): component Proportion (mol %) SiO ₂ 1.0 - 16.5 _{B2O3 _} 0.0-13.5 _{Al2O3 _} 0.0 - 3.0 BaO 1.0 - 20.0 ZnO 0.0 - 5.0 _{La2O3 _} 5.0 - 20.0 TiO ₂ 28.0 - 65.0 _{Nb2O5 _} 0.1 -20.0 _{Gd2O3 _} 0.0 - 8.0 WHERE ₃ 0.0 - 5.0 _{Y2O3 _} 0.0 - 5.0 ZrO ₂ 1.0 - 11.0 Σ La ₂ O ₃ + Y ₂ O ₃ + Gd ₂ O ₃ + Yb ₂ O ₃ + Lu ₂ O ₃ 12.5 - 20.0

The glass article can in particular comprise or consist of a glass which comprises or consists of the following components in the specified proportions (in mol %): component Proportion (mol %) SiO ₂ 1.0 - 16.5 _{B2O3 _} 0.0-13.5 _{Al2O3 _} 0.0 - 3.0 BaO 1.0 - 20.0 ZnO 0.0 - 5.0 _{La2O3 _} 5.0 - 20.0 TiO ₂ 28.0 - 65.0 _{Nb2O5 _} 0.1 -20.0 _{Gd2O3 _} 0.0 - 8.0 WHERE ₃ 0.0 - 5.0 _{Y2O3 _} 0.0 - 5.0 ZrO ₂ 1.0 - 11.0 _K2O 0.0 - 1.5 CaO 0.0 - 1.5 component Proportion (mol %) SrO 0.0-1.5 _{Ta2O5 _} 0.0-1.5 _{Yb2O3 _} 0.0-1.5 _{Lu2O3 _} 0.0 - 5.0 Σ SiO ₂ + B ₂ O ₃ 3.5 - 25.0 Σ La ₂ O ₃ + Y ₂ O ₃ + Gd ₂ O ₃ + Yb ₂ O ₃ + Lu ₂ O ₃ 12.5 - 20.0

The glass article can in particular comprise or consist of a glass which comprises or consists of the following components in the specified proportions (in mol %): component Proportion (mol %) SiO ₂ 1.5 - 16.0 _{B2O3 _} 0.5-13.0 _{Al2O3 _} 0.0 - 2.5 BaO 2.0 - 18.0 ZnO 0.0-4.0 _{La2O3 _} 7.0-18.0 TiO ₂ 30.0 - 62.5 _{Nb2O5 _} 0.5 - 18.0 _{Gd2O3 _} 0.0 - 7.0 WHERE ₃ 0.0 - 4.0 _{Y2O3 _} 0.0 - 4.0 ZrO ₂ 2.0 - 10.0 _K2O 0.0 - 1.2 CaO 0.0 - 1.2 SrO 0.0 - 1.2 _{Ta2O5 _} 0.0 - 1.2 _{Yb2O3 _} 0.0 - 1.2 _{Lu2O3 _} 0.0 - 4.0 Σ SiO ₂ + B ₂ O ₃ 5.0 - 22.5 Σ La ₂ O ₃ + Y ₂ O ₃ + Gd ₂ O ₃ + Yb ₂ O ₃ + Lu ₂ O ₃ 13.5 - 19.0

The glass article can in particular comprise or consist of a glass which comprises or consists of the following components in the specified proportions (in mol %): component Proportion (mol %) SiO ₂ 1.5 - 16.0 _{B2O3 _} 0.5-13.0 _{Al2O3 _} 0.0 - 2.5 BaO 2.0-18.0 ZnO 0.0 - 4.0 _{La2O3 _} 7.0 - 18.0 TiO ₂ 30.0 - 62.5 _{Nb2O5 _} 0.5 - 18.0 _{Gd2O3 _} 0.0 - 7.0 WHERE ₃ 0.0 - 4.0 _{Y2O3 _} 0.0 - 4.0 ZrO ₂ 2.0 - 10.0 Σ La ₂ O ₃ + Y ₂ O ₃ + Gd ₂ O ₃ + Yb ₂ O ₃ + Lu ₂ O ₃ 13.5 - 19.0

The glass article can in particular comprise or consist of a glass which comprises or consists of the following components in the specified proportions (in mol %): component Proportion (mol %) SiO ₂ 2.5 - 15.5 _{B2O3 _} 1.0-12.5 _{Al2O3 _} 0.0 - 2.0 BaO 3.0 - 17.0 ZnO 0.0 - 3.0 _{La2O3 _} 8.0 - 17.0 TiO ₂ 32.0 - 60.0 _{Nb2O5 _} 1.0-17.0 _{Gd2O3 _} 0.0 - 6.0 WHERE ₃ 0.0 - 3.0 _{Y2O3 _} 0.0 - 3.0 component Proportion (mol %) ZrO ₂ 3.0 - 9.5 Σ La ₂ O ₃ + Y ₂ O ₃ + Gd ₂ O ₃ + Yb ₂ O ₃ + Lu ₂ O ₃ 14.0 - 18.0

The glass article can in particular comprise or consist of a glass which comprises or consists of the following components in the specified proportions (in mol %): component Proportion (mol %) SiO ₂ 2.5 - 15.5 _{B2O3 _} 1.0-12.5 _{Al2O3 _} 0.0 - 2.0 BaO 3.0-17.0 ZnO 0.0 - 3.0 _{La2O3 _} 8.0-17.0 TiO ₂ 32.0 - 60.0 _{Nb2O5 _} 1.0 - 17.0 _{Gd2O3 _} 0.0 - 6.0 WHERE ₃ 0.0-3.0 _{Y2O3 _} 0.0 - 3.0 ZrO ₂ 3.0 - 9.5 Σ SiO ₂ + B ₂ O ₃ 3.5 - 25.0 Σ La ₂ O ₃ + Y ₂ O ₃ + Gd ₂ O ₃ + Yb ₂ O ₃ + Lu ₂ O ₃ 14.0 - 18.0

The glass article can in particular comprise or consist of a glass which comprises or consists of the following components in the specified proportions (in mol %): component Proportion (mol %) SiO ₂ 2.5 - 15.5 _{B2O3 _} 1.0-12.5 _{Al2O3 _} 0.0 - 2.0 BaO 3.0-17.0 ZnO 0.0 - 3.0 _{La2O3 _} 8.0-17.0 TiO ₂ 32.0 - 60.0 component Proportion (mol %) _{Nb2O5 _} 1.0 - 17.0 _{Gd2O3 _} 0.0 - 6.0 WHERE ₃ 0.0 - 3.0 _{Y2O3 _} 0.0 - 3.0 ZrO ₂ 3.0 - 9.5 _K2O 0.0 - 1.0 CaO 0.0 - 1.0 SrO 0.0 - 1.0 _{Ta2O5 _} 0.0 - 1.0 _{Yb2O3 _} 0.0 - 1.0 _{Lu2O3 _} 0.0 - 3.0 Σ La ₂ O ₃ + Y ₂ O ₃ + Gd ₂ O ₃ + Yb ₂ O ₃ + Lu ₂ O ₃ 14.0 - 18.0

The glass article can in particular comprise or consist of a glass which comprises or consists of the following components in the specified proportions (in mol %): component Proportion (mol %) SiO ₂ 2.5 - 15.5 _{B2O3 _} 1.0-12.5 _{Al2O3 _} 0.0 - 2.0 BaO 3.0-17.0 ZnO 0.0 - 3.0 _{La2O3 _} 8.0 - 17.0 TiO ₂ 32.0 - 60.0 _{Nb2O5 _} 1.0-17.0 _{Gd2O3 _} 0.0 - 6.0 WHERE ₃ 0.0 - 3.0 _{Y2O3 _} 0.0 - 3.0 ZrO ₂ 3.0 - 9.5 _K2O 0.0 - 1.0 CaO 0.0 - 1.0 SrO 0.0 - 1.0 component Proportion (mol %) _{Ta2O5 _} 0.0-1.0 _{Yb2O3 _} 0.0-1.0 _{Lu2O3 _} 0.0 - 3.0 Σ SiO ₂ + B ₂ O ₃ 3.5 - 25.0 Σ La ₂ O ₃ + Y ₂ O ₃ + Gd ₂ O ₃ + Yb ₂ O ₃ + Lu ₂ O ₃ 14.0 - 18.0

The glass article can in particular comprise or consist of a glass which comprises or consists of the following components in the specified proportions (in mol %): component Proportion (mol %) SiO ₂ 3.0 - 15.0 _{B2O3 _} 1.5-12.0 _{Al2O3 _} 0.0 - 1.5 BaO 4.0-16.0 ZnO 0.0 - 2.0 _{La2O3 _} 8.5-16.0 TiO ₂ 34.0 - 59.0 _{Nb2O5 _} 2.0 - 16.0 _{Gd2O3 _} 0.0 - 5.0 WHERE ₃ 0.0 - 2.0 _{Y2O3 _} 0.0 - 2.0 ZrO ₂ 4.0 - 9.0 _K2O 0.0 - 0.5 CaO 0.0 - 0.8 SrO 0.0 - 0.8 _{Ta2O5 _} 0.0 - 0.5 _{Yb2O3 _} 0.0 - 0.5 _{Lu2O3 _} 0.0 - 2.0

The glass article according to the invention can, for example, have a refractive index n _G of at least 1.95, at least 1.96, at least 1.97, at least 1.98, at least 1.99, at least 2.00, at least 2.01, at least 2.02, at least 2.03, at least 2.04, or at least 2.05, in particular at least 2.06, at least 2.07, at least 2.08, at least 2.09, or at least 2.10, at least 2.11 or at least 2 .12. The glass article according to the invention can, for example, have a refractive index n _G of at most 2.25, at most 2.24, at most 2.23, at most 2.22, at most 2.21, at most 2.20, at most 2.19, at most 2.18, at most 2.17, at most 2.16, or at most 2.15. The glass article according to the invention can, for example, have a refractive index n _G in a range from 1.95 to 2.25, from 1.96 to 2.24, from 1.97 to 2.23, from 1.98 to 2.22, from 1 .99 to 2.21, from 2.00 to 2.20, from 2.01 to 2.19, from 2.02 to 2.18, from 2.03 to 2.17, from 2.04 to 2, 16, or from 2.05 to 2.16, or from 2.10 to 2.16, or from 2.12 to 2.15. The refractive index n _G can in particular be in a range from 2.06 to 2.25, from 2.07 to 2.24, from 2.08 to 2.23, from 2.09 to 2.22, from 2.10 to 2.21, from 2.11 to 2.20 or from 2.12 to 2.19.

The glass article of the present invention may, for example, have a thickness in a range from 0.05 to 3.0 mm, from 0.1 to 2.75 mm, from 0.15 to 2.5 mm, from 0.2 to 2.25 mm, from 0.25 to 2.0 mm, from 0.3 to 1.8 mm, from 0.35 to 1.5 mm, from 0.4 to 1.0 mm or from 0.5 to 0.8 mm . The thickness of the glass article can be, for example, at least 0.05 mm, at least 0.1 mm, at least 0.15 mm, at least 0.2 mm, at least 0.25 mm, at least 0.3 mm, at least 0.35 mm, at least 0 .4 mm or at least 0.5 mm. The thickness of the glass article can be, for example, at most 3.0 mm, at most 2.0 mm, at most 1.8 mm, at most 1.5 mm, at most 1.0 mm or at most 0.8 mm. The glass article can in particular be a wafer, a plate, a pane or a spectacle lens or a part thereof.

The glass article can have, for example, a surface roughness (roughness squared (R _q or also RMS)) of at most 5 nm, at most 3 nm, at most 1 nm, preferably <1 nm, preferably <0.5 nm, or <0.1 nm. The peak-to-valley height R _t is preferably at most 6 nm, more preferably at most 4 nm and particularly preferably at most 2 nm, for example at most 1 nm, at most 0.5 nm or at most 0.1 nm. The peak-to-valley height and/or the square roughness are preferred according to EN ISO 4287 determined, in particular in accordance with DIN EN ISO 4287:2010-07 . The peak-to-valley height and/or the quadratic roughness can be determined, for example, using an atomic force microscope (AFM). The test area can be 2×2 μm ² or 10×10 μm ² , for example.

The glass article can have a Knoop hardness of >600, preferably >630, particularly preferably >650, for example. For example, the Knoop hardness may be 900 at most, 850 at most, or 820 at most. The Knoop hardness can be in a range from >600 to 900, from >630 to 850, or from >650 to 820, for example.

A glass article according to the present invention can be produced in particular by means of a method comprising shaping with defined cooling rates.

The present invention also relates to the use of a glass article according to the invention as a wafer for augmented reality applications, in smartphone cameras and/or as a waveguide coupler.

Description of the figures

1 shows the measured values of the refractive index and, as a dashed curve, the fit of the measured data to Equation 1. From this, λ _max can be determined in a determinate manner.

examples

The compositions of example glasses according to the invention are shown in the following tables (in mol %). Also shown are the refractive index n _G and the R number.

In the following, it is explained, using example glass 31, as an example of how the R number according to the invention can be determined.

The refractive index of example glass 31 was measured at three different wavelengths. The results are in the following table and in 1 shown. λ [nm] refractive index 441 2.2040 639 2.1239 947 2.0896

By adapting/fitting equation 1, the parameters λ _max and c were determined using the least squares method. With the refractive indices n _i measured at the wavelengths λ _i ,

Σ _i (n _i -n(λ _i )) ² → 0 minimized, where according to equation 1 $n\left(\lambda \right)=c\cdot \text{ln}\left[\frac{{\lambda }^2-{\lambda }_{min}^2}{{\lambda }^2-{\lambda }_{max}^2}\cdot \frac{{\lambda }_{max}^2}{{\lambda }_{min}^2}\right]+1\text{is}.$

The parameter λ _min = 33 nm was assumed to be constant.

From the fit, λ _max = 289.9 nm and c = 0.25 were determined.

The refractive index n _G was 2.1359.

mit λ_R= 656 nm, λ_G = 587 nm und λ_B = 486 nm ergibt sich R = 0,973.From the formula $$R=\left(n_G-1\right)\left(\frac{\text{ln}\left[\frac{{\lambda }_G{}^2-{\lambda }_{min}^2}{{\lambda }_G^2-{\lambda }_{max}^2}\cdot \frac{{\lambda }_{max}^2}{{\lambda }_{min}^2}\right]}{42\text{ln}\left[\frac{{\lambda }_B^2-{\lambda }_{min}^2}{{\lambda }_B^2-{\lambda }_{max}^2}\cdot \frac{{\lambda }_R^2-{\lambda }_{max}^2}{{\lambda }_R^2-{\lambda }_{min}^2}\right]}+\frac{1}{2.8}\right)$$

with λ _R = 656 nm, λ _G = 587 nm and λ _B = 486 nm we get R = 0.973.

QUOTES INCLUDED IN DESCRIPTION

This list of documents cited by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Non-patent Literature Cited

• DIN EN ISO 4287 [0058]
• DIN EN ISO 4287:2010-07 [0058]

Claims (10)

Glass articles with a refractive index n _G ≥ 1.95 and an R number in a range from 0.900 to 1.050, where the R number is calculated according to the following formula $$R=\left(n_G-1\right)\left(\frac{\text{ln}\left[\frac{{\lambda }_G{}^2-{\lambda }_{min}^2}{{\lambda }_G^2-{\lambda }_{max}^2}\cdot \frac{{\lambda }_{max}^2}{{\lambda }_{min}^2}\right]}{42\text{ln}\left[\frac{{\lambda }_B^2-{\lambda }_{min}^2}{{\lambda }_B^2-{\lambda }_{max}^2}\cdot \frac{{\lambda }_R^2-{\lambda }_{max}^2}{{\lambda }_R^2-{\lambda }_{min}^2}\right]}+\frac{1}{2.8}\right)$$

where λ _R = 656 nm, λ _G = 587 nm and λ _B = 486 nm, where λ _min = 33 nm and where n _G is the refractive index at a wavelength of 587 nm. glass items claim 1 consisting of a glass comprising the following components in the specified proportions (in mol%): component Proportion (mol %) SiO ₂ 1.0 - 16.5 _{B2O3 _} 0.0-13.5 _{Al2O3 _} 0.0 - 3.0 BaO 1.0 - 20.0 ZnO 0.0 - 5.0 _{La2O3 _} 5.0 - 20.0 TiO ₂ 28.0 - 65.0 _{Nb2O5 _} 0.1 - 20.0 _{Gd2O3 _} 0.0 - 8.0 WHERE ₃ 0.0-5.0 _{Y2O3 _} 0.0 - 5.0 ZrO ₂ 1.0 - 11.0 Σ La ₂ O ₃ + Y ₂ O ₃ + Gd ₂ O ₃ + Yb ₂ O ₃ + Lu ₂ O ₃ 12.5 - 20.0 Glass article according to at least one of the preceding claims having a refractive index n _G in a range from 2.00 to 2.20. Glass article according to at least one of the preceding claims, wherein the glass article has a thickness in a range from 0.2 to 3.0 mm. Glass article according to at least one of the preceding claims with a surface roughness R _q of <1 nm, preferably <0.5 nm. Glass article according to at least one of the preceding claims with a Knoop hardness of > 600, preferably > 630, particularly preferably > 650. Glass article according to at least one of the preceding claims, wherein the internal transmission τ _i at a wavelength of 460 nm and a layer thickness d of 1 cm is > 0.9. Glass article according to at least one of the preceding claims, wherein the R number is in a range from > 0.965 to < 0.985. Glass article according to at least one of the preceding claims, wherein the ratio of the sum of the proportions of SiO ₂ and B ₂ O ₃ (in mol %) to the sum of the proportions of La ₂ O ₃ , Y ₂ O ₃ , Gd ₂ O ₃ , Yb ₂ O ₃ and Lu ₂ O ₃ (in mol %) ranges from 0.5:1 to 1.3:1. Use of a glass article according to at least one of Claims 1 until 8th as a wafer for augmented reality applications, in smartphone cameras and/or as a waveguide coupler.

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